Record-breaking relay

Tianna Madison (left), Bianca Knight, Carmelita Jeter and Allyson Felix brought home gold for the United States in the women's 4x100-meter relay, smashing a world record in the process. Their time of 40.82 seconds broke the old mark of 41.37 -- which had stood since 1985.-- Rick Porter, Zap2it

Tianna Madison (left), Bianca Knight, Carmelita Jeter and Allyson Felix brought home gold for the United States in the women's 4x100-meter relay, smashing a world record in the process. Their time of 40.82 seconds broke the old mark of 41.37 -- which had stood since 1985.-- Rick Porter, Zap2it (Getty Images)

Tianna Madison (left), Bianca Knight, Carmelita Jeter and Allyson Felix brought home gold for the United States in the women's 4x100-meter relay, smashing a world record in the process. Their time of 40.82 seconds broke the old mark of 41.37 -- which had stood since 1985.-- Rick Porter, Zap2itGetty Images